GB-A-2 172 677 already discloses an assembly of a pressurized fluid mechanism, motor or pump, and of a disc brake which is coupled thereto, comprising a principal housing; a reaction cam; a cylinder-block mounted for relative rotation with respect to said cam about a geometrical axis and provided with a supply face; a plurality of cylinders arranged in the cylinder-block, substantially radially with respect to said geometrical axis; a plurality of pistons, mounted to slide in said cylinders and capable of being in abutment on said cam, preferably via roller bearings; an internal fluid distributor valve, substantially stationary, vis-a-vis rotation about said geometrical axis, with respect to said cam and provided with a communication face capable of being disposed in abutment on said supply face of the cylinder-block, the substantially tight mutual abutment of said supply and communication faces defining within the principal housing two enclosures separated by said supply and communication faces; a first disc brake element, such as a shaft, fast with respect to rotation about said geometrical axis, with a first of the two parts--cylinder block and cam--and bearing a first set of disc brakes; a second disc brake element, such as a brake housing, fast with respect to rotation about said geometrical axis, with the second of the said two parts--cylinder-block and cam--, and bearing a second set of brake discs; a thrust member, capable of being in abutment on a brake disc disposed at the end of a stack constituted by the assembly of the brake discs of said first and second sets of brake discs; a motive braking member, coupled to said thrust member and capable of causing a braking thrust displacement on said stack of brake discs; and a brake-release jack, coupled between said thrust member and said second disc brake element and comprising a brake-release chamber capable of containing a brake-release fluid under pressure, whose effect is the elimination of the braking thrust on said stack.
In the known mechanisms, the disc brake is entirely distinct from the pressurized fluid mechanism and is generally coupled thereto by the fixation of the brake housing on the principal housing of the mechanism. The shaft is contained in the two, principal and brake, housings, but an O-ring is disposed between one of the two housings and the shaft, completing total separation of the brake and of the mechanism. In addition, this O-ring is subject to dynamic forces between two parts mounted for relative rotation and must consequently present particular characteristics which are relatively expensive.
One of the objects of the invention is the elimination of this O-ring and its arrangements for assembly, and is materialized by the arrangement whereby the brake-release chamber is in permanent communication with a first of said two enclosures, therefore isolated from the second enclosure by mutual abutment of the supply face of the cylinder-block and of the communication face of the distributor valve.
The following advantageous arrangements are, in addition, preferably adopted:
said enclosures are separated in tight manner;
said second enclosure contains the bearing rollers of the pistons on the cam and is connected to a reservoir of non-pressurized fluid.
According to the invention, the fluid contained in the brake-release chamber also fills at least part of the motor housing until it bathes the edge of the substantially tight abutment of the supply face of the cylinder-block and communication face of the internal distributor valve.
There is therefore now only one fluid and the elimination of the O-ring disposed previously between the central shaft and one of the housings results in a simplified mechanism and a reduced cost price thereof.
The fluid which, according to the invention, is now capable of bathing at least one of the edges of the tight abutment between the cylinder-block and the internal distributor valve, brings the following additional advantages:
this fluid is adapted to produce a counter-pressure in the zone of said edge, and therefore to reduce the leakages of supply fluid of the cylinders which occur between said supply and communication faces, which is advantageous per se, and precious in closed circuits, as the characteristics of the booster pump of such a closed circuit are linked with the flowrate of said leakages: a reduction in the flowrate of the leakages enables a smaller booster pump, therefore less expensive, to be chosen;
this fluid is in addition adapted to irrigate the mechanism, i.e. remove excess calories therefrom or, on the contrary, heat it, depending on the existing operational conditions.